1. Field of the Invention
The invention relates to the manufacture and use of functionalized polymers capable of interacting with fillers.
2. Background of the Invention
Tire treads, power belts, and the like often are made from compositions that contain one or more elastomers and one or more reinforcing materials such as, for example, particulate carbon black and silica. For a general discussion of this topic, see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.
Safety and durability considerations mandate that tire treads provide both good traction and resistance to abrasion; however, motor vehicle fuel efficiency concerns argue for a minimization in their rolling resistance, which correlates with a reduction in hysteresis and heat build-up during operation of the tire. The foregoing considerations are, to a great extent, competing and somewhat contradictory: a tire tread composition designed to improve tread traction on the road usually results in increased rolling resistance and vice versa.
Typically, filler(s), elastomer(s), and additives are chosen so as to provide an acceptable balance of these properties. Ensuring that constituent reinforcing filler(s) are well dispersed throughout the elastomeric material(s) in such compositions both enhances processability and acts to improve physical properties such as, e.g., compound Mooney viscosity, elastic modulus, tan δ, and the like. Resulting articles made from such compositions can exhibit desirable properties such as reduced hysteresis, reduced rolling resistance, and good traction on wet pavement, snow and ice.
Increasing the interaction with elastomer(s) is one way to improve their dispersion. Examples of efforts of this type include high temperature mixing in the presence of selectively reactive promoters, surface oxidation of the compounding materials, surface grafting, and chemical modifications to the terminal ends of the polymers with, e.g., amines, tin compounds, and the like.
Because elastomers used in such compositions often are anionically polymerized, attachment of certain functional groups, particularly amines, is difficult. This is because living polymers are terminated by active hydrogen atoms such as are present in, e.g., hydroxyl groups, thiol groups, and particularly primary and secondary amine groups. This undesired termination can be avoided through use of reaction schemes that allow for attachment of non-amine N-containing compounds followed by conversion to amines, i.e., indirect attachment schemes.
Continued hysteresis reduction and provision of a direct mechanism for attaching amine functionality to a living polymer both remain highly desirable.